Performance of water-borne paint formulations is influenced in part by the surface chemistry of the inorganic pigment used to opacify the paint. Pigments such as the widely used TiO2 tend to be hydrophilic in their native state and therefore not particularly effective as a barrier to penetration of water and water-soluble colorants at the pigment-binder interface. For this reason, it would be advantageous to modify the surface of inorganic pigment particles to provide coatings with improved resistance to stains and corrosion.
The dispersion stability of pigment particles in the paint formulation affects the hiding efficiency of the consequent film. Pigment aggregates provide less hiding than isolated primary particles; therefore, it would be further advantageous to modify the surface of pigment particles to minimize pigment aggregation in films, thereby reducing the amount of pigment needed in the formulation.
It is known in the art to modify the surface of pigment particles with hydrophobic groups. In theory, hydrophobically modified pigment particles would be expected to improve barrier properties and more strongly associate with binder particles in a latex, thereby improving hiding. Nevertheless, in practice, formulators experience great difficulty in dispersing hydrophobically modified pigment particles in water because of their poor wettability. Accordingly, it would be an advance in the art of pigmented water-borne coatings formulations to discover a hydrophobically modified pigment that are readily dispersible in water.